1. Brewing Your
Own Game
Engine
The Pros & Cons of Using Open Source Software to
Rapidly Develop Cross-platform Indie Games and Tools
Ye Feng

2. What’s In The Talk
• No rocket science
From practical experience
• Arguable

3. Who We Are

4. Project OneTap
2D Action
One Casual
Button Simple
Puzzle
Customizable
Levels

5. Challenge:
Level Design
Level Design

6. Wise Man Builds His
House On The Rock
• Option 1: Cheap Commercial Engine
• Option 2: Open Source Engine

7. Cheap Commercial
Engine
• Pros
Cons
IDE
• Offline IDE
• Cross
platform(when
• Portability(when not
officially officially supported)
supported) • No source code
Moderate • Pure script driven
license fee

8. Open Source Engine
• Pros Cons
Source code • No IDE
• Cross • Pure native code
platform driven
Free • Open Source
License

9. Choice
• Option 1: Cheap Commercial Engine
Option 2: Open Source Engine
• Option 3: Open Source Engine + Game
Support Layer
• Allegro ✔
• http://alleg.sourceforge.net/

10. Demo

11. Why
• Script + native code
IDE for specific game type
• In-game editor
• Performance
• etc...

12. What’s In It
• Game Object System
Script Integration
• Physics Integration
• Content pipeline tools
Others
• Simple Scene Management
• Action System
Script Key-Value Dictionary
• etc...

13. Game Object System

14. Inheritance &
Gameplay Development
• Gameplay dev nature: iteration
Iteration causes changes
• Inheritance: not change-friendly

15. Good

16. Bad

22. Hypothesis:
Composition

23. Design Pattern
Favor object composition over class
inheritance

24. Game Object &
Game Component
• Composition instead of inheritance
A object of gameplay logic
• Is composed by multiple functional
components
Component #1
Game Component #2
Object
Component #3

25. Game Object &
Game Component
• Add/remove component in runtime
• Key to build an IDE

26. Composition To The
Rescue

27. Basic Components
• Positioning info: Transform
2D rendering: Sprite
• Bitmap info: Bitmap Source
• Input processing: Event Receiver
Rigid body entity: Body
• Collider entity: Fixture
• Particle effect: Particle Emitter
• etc...

28. User Components
• Arbitrary stuff that gameplay needs
Rotation forever
• A goal in level
• The behavior of characters
A spike need to be avoided
• Line drawer needed by editor
etc...

29. Demo

30. Script Integration

31. Dilemma of Native
• Compilation time
• Runtime modification
• Advanced language feature
• “Glue” code

32. 2-tiers System To
The Rescue
• Core: native code
• Editor and gameplay: script
• Lua

33. Related Works
• Communication between native and
script
• Export tools/libraries
• Script API

34. Communication -
Native & Script
• Simple interfaces/engine API
• tolua
• http://www.tecgraf.puc-rio.br/~celes/
• Simple, no compilation cost
• Complex interfaces
• Lua C API

35. Related Works cont.
• Serialization
• Load/save, editor
• Support for advanced features
• Reference
• Function object, closure
• etc...

36. Serialization
• Pluto
• https://github.com/hoelzro/pluto
• Write serialization code for every
component
• 1000 lines of Lua code

37. Prefabricated Object
• Take snapshot of object
• Parameters
• References
• Hierarchy
• Assisted object design
• Level editor ➔ object editor

38. Patching
Patching binary ➔ patching data

39. Demo

40. Content Pipeline
Tools

41. DCC Tools
Flash?

42. Pipeline
Flash
☹
Export IDE
Animation Manually
Created
Atlas
Game
Photoshop
Static

43. Solution
• swfdec
• Open source Flash player
• LGPL
• swfdec-dumper
• Surface ➔ disk
• https://github.com/fengye/swfdec-dum

44. Pipeline 2.0
☺
Flash swfdec
☹
Animation dumper Manually
IDE
Created
Atlas
Game
Photoshop
Static

45. Atlas Tool
• Stitch bitmap into Atlas
• Automation
• Transparent process

46. Texture Atlas Gen
• nVidia Texture Atlas Tools
• File format support☺
• Mipmap☺
• Free☺
• Only for sprite sheets☹
• Pack algorithm

47. Pipeline 3.0
☺
Flash swfdec
dumper ☺
Animation Texture IDE
Atlas
Gen
Photoshop Game
Static

48. Questions?

49. Issues
• Debugger
• Coroutine/fiber
• Reference leak
• Script loader

50. Communication
Between Components
• Query for interface
• Increase coupling
• Register message
• Order of notification is not defined

51. iPhone Version

52. Naive Port
• Mac➔iPhone
• 20 FPS + Crashes
• Possible causes:
• Memory out of bound
• Script slowdown
• Performance of rendering

53. Memory Limitation
• Unified memory architecture
• User program up to 112M - iPhone 4

54. Beyond Memory
Limitation
• 2D Games - bitmap texture heavy
Preallocate bitmap space
• 22 x 1M x 4 bpp = 88M
• Atlas
Stitch small bitmap into atlas
• Automation tool is a must

55. Beyond Memory
Limitation
• Memory fragmentation
Heap allocation & deallocation
• Script
• dmalloc
• Drop-in, just works

56. Detect Perf. Issue
• Instruments
Mac/iPhone
• Code intrusive profiler

57. Detect Perf. Issue
• Found by intrusive profiler:
High draw call count
• Found by instruments:
• Renderer utilization 100%
• Tiler utilization 9 ％

58. Reduce Draw Call
• Common trick in desktop app
Implementation
• Collect draw calls
• Sort, cluster calls with same
bitmap
Batch draw
• Target: reduce pipeline stall caused
by switching textures

59. Reduce Draw Call
• Before
• After

60. Rendering
Optimization
• Fillrate
Number of texels written to
memory per second
• Desktop app, pixel-shader heavy
• Fillrate bottleneck
✔ • Reduce framebuffer size ➔ boost
frame rate

61. Fillrate Optimization
• Hardware limit: 221M/sec
60 FPS: 3.6M/frame
• 30 FPS: 7.2M/frame
• 2D Game
Alpha-blend heavy
• Hard to utilize Z-buffer

62. Fillrate Optimization
• Reduce overdraw
Use Z-buffer for strictly opaque
objects
• Modify art asset guideline

63. Demo